The present invention relates to a method of manufacturing a unitary structural body, without a gap, from plural body members having a flange by joining an end portion of one plate to an end portion of another plate; and, in particular, the invention relates to a method of manufacture suitable for production of an end structure constituting an end portion of a railway vehicle.
As shown in Japanese patent No. 2,692,459 (U.S. Pat. No. 5,488,770), a car body of a railway vehicle typically has a hexahedron-shaped body. An end portion of the railway vehicle is referred to as an end structure. In the end structure, there is provided a passage or door for allowing passengers to come and go to an adjacent car.
For this reason, the end structure requires two plates constituting a panel on the right side of the passage and a panel on the left side of the passage and a plate for constituting a panel above the passage. Since the three plates join a roof structural body member and a side structural body member, the outer side edges of the three plates each have a flange. Further, the end portions of the three plates have reinforcement flanges.
In the prior art, a product in the form of a plate having a flange along a side of the plate is manufactured by press forming, in which the plate is placed between a female die and a male die. Since a female die and a male die are required for such processing, the cost of manufacture becomes high.
For the above reason, respective L-shaped plates are welded using spot welding and one side of the L-shaped plate forms the above-stated flange.
As a means for avoiding the need for a male metal die, a forming method using only a female die has been proposed, as shown in FIG. 18 to FIG. 20 of Japanese application patent laid-open publication No. Hei 11-310,371. In this method, on the female die, an outer peripheral portion of a plate of raw material is fixed and the raw material is pushed in using a rod shape tool moving along an inner peripheral face of the female die. The tool is moved and the plate is subjected incrementally to a buckling processing.
On the other hand, in Japanese application patent laid-open publication No. Hei 10-76,321, a method is disclosed in which a squeezing processing is carried out incrementally.
The construction shown in FIG. 13 will be explained by way of example. On three plates 1, 2, 3, after flanges 1b, 1c, 1d, 2b, 2c, 2d, 3b, 3c, 3d have been provided. The flanges 1b, 2b of the right and the left plates 1, 2 are overlapped, and these flanges 1b, 2b are subjected to spot welding and are formed as one body. The flanges are provided as an integral part of the body by bending the plates 1, 2, 3. Further, the flanges 1c, 3c, 2c are overlapped by a roof structural body 30 and welded.
The reference numeral 45 denotes a passageway for passengers. The respective three plates 1, 2, 3 are continued to the adjacent flange and the connection portion has a circular arc shape. In this case, to a joining portion between the right and the left plates 1, 3, the central plate 2 and the roof structural body 30, a space exists. This space must be closed with another plate to prevent rain and other elements for entering the space. The closing work requires a high cost. Further, the outer appearance becomes unattractive.
Further, the flanges are formed by bending the plate, so that a cross-section thereof has the circular arc shape. For this reason, a groove is provided between the right and left plates, with the result that the outer appearance becomes unattractive.
In the incremental forming method, since the metal die is in the form of a single die, the manufacture can be carried out with a low cost. However, in the incremental forming method, as described in the above-stated Japanese application patent laid-open publication Hei 11-310,371, the flange is formed to the end portion, but the plate is left on the outer peripheral portion of the flange. Thus, in a case where the plate is unnecessary, it is necessary to cut off and remove the outer peripheral portion of the flange.
Further, according to this incremental forming method, when the flange is formed, the angle between the flange and the bottom plate is not a right angle, however it works. For example, when a cylinder is joined by overlapping the flange, and the flange has a right angle, it is difficult to carry out overlapping joining.
Further, it is difficult to form a flange having a substantial height. For this reason, it is difficult to overlap the flange of one member and a flange of another member.
On the other hand, according to the processing method described in the above-stated Japanese application patent laid-open publication No. Hei 10-76,321, when the flange is processed, a wrinkle can occur easily in the joining portion between the one flange and the other flange.